The present invention relates to screw presses for extracting liquids from liquid containing materials and especially to a screw press for the extraction of juice from pulp in fruits and vegetables or the like.
A variety of screw presses for the extraction of liquids from solids or semi-solids has been used in various food industries. Typically, these presses feed fruit or vegetables, whole or in chunks, from a hopper into a rotating screw which conveys the fruit from the hopper forward through the press barrel or cage. The material is compacted against the inner cage surface by various structures, and juices are squeezed from the fruit or vegetables, passing through screens formed in the cage wall, then collected for further processing. The passage between the cage wall and the screw may be narrowed by increasing the diameter of the screw body so the volume between the screw flight will be reduced as the material moves along the screw, or alternatively by reducing the pitch of the screw.
In U.S. Pat. Nos. 3,135,193; 3,256,807; and 3,266,808, improvements to screw presses of this type are disclosed having a rotating compressing screw in which the shank or base of the screw increases in diameter rapidly at one point, such that an abrupt outwardly progressing portion of the screw causes a localized crushing force against the material being fed through this part of the press. After the abrupt crushing, the passage remains substantially constant in cross-section for a relatively short distance, then the dried pulp exits from the press at the end of the screw. The exit or discharge in these prior patents uses a spring loaded flipper door which allows the egress of the material only when the pressure exceeds predetermined forces.
Another form of dewatering press is that sold by a French company, Societe Pour L'Equipment des Industries Chimiques, of Paris, France, often referred to as SPEICHIM. This press employs two screws in series, with flights of opposite pitch, separately driven by coaxial shafts from a single gear box. The screws are counter-rotated such that both act to advance material through the press, and the second screw (in the direction of material flow) exerts the higher pressure, discharging into a final chamber which has drainage openings both through the cage walls and a central drainage cylinder. A cone member, hydraulically adjustable, is mounted coaxially of the drainage cylinder and controls the discharge opening or exit from the final chamber.
The present invention eliminates the flipper doors and directs the pulp or cake material into a receiving chamber where the material builds up and is removed from the chamber through an exit or discharge opening by an independent auger or conveyor screw aligned with the pressure screw and having a separate motor drive.